Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
As a result, kinds of applications using the secondary battery are being increased owing to advantages of the secondary battery, and hereafter the secondary battery is expected to be applied to more applications and products than now.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
The size and weight of a battery module is directly related to an accommodation space and output of a corresponding middle or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, lightweight battery modules. Furthermore, for devices, such as electric bicycles and electric vehicles, which are subject to a large number of external impacts and vibrations, require stable electrical connection and physical coupling between components constituting the battery module. In addition, a plurality of battery cells is used to accomplish high output and large capacity, and therefore the safety of the battery module is regarded as important.
Preferably, the battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on such a pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, and the manufacturing cost of the pouch-shaped battery is low.
FIG. 1 is a perspective view typically showing a conventional representative pouch-shaped battery cell. Referring to FIG. 1, a pouch-shaped battery cell 10 is configured to have a structure in which two electrode terminals 11 and 12 protrude from the upper end and the lower end of a battery cell body 13, respectively, such that the electrode terminals 11 and 12 are opposite to each other. In a state in which an electrode assembly (not shown) is mounted in a battery case 14, opposite sides 14a and upper and lower ends 14b and 14c of the battery case 14 are bonded, whereby the pouch-shaped battery cell 10 is manufactured.
In order to connect pouch-shaped battery cells in series and/or in parallel to each other, the electrode terminals of the pouch-shaped battery cells are connected to each other via connection members, such as bus bars, for achieving electrical connection between the pouch-shaped battery cells. In this case, additional electrical connection members are needed. Furthermore, the total size of each of the battery cells is increased, and the structure of each of the battery cells is complicated, since the members are mounted to the battery cells.
Therefore, there is a high necessity for a battery cell that can be electrically connected to another battery cell without additional electrical connection members and a battery module including the same.